Crustacean meat and in particular crab leg meat is commonly sold for human consumption in an "the shell" form. It is important from a marketing perspective that the exterior surfaces of the shell be cleaned and free of debris. The upper sides of crab legs, i.e., the side that faces upwardly when the crabs are in their normal crawling position, normally is red in color. This color is imparted by a relatively delicate layer on the crab shell, which is easily abraded away during cleaning and processing. It is important from a commercial perspective that the red layer be left substantially intact and unblemished, and that it also be clean and free of slime, slub and other debris.
Applicants' co-pending Canadian Patent application numbers 2,206,678 and 2,234,034 relate to apparatus for cleaning the shells of crustaceans, and in particular for cleaning crab legs. This apparatus is substantially fully automated, whereby an operator positions individual crabs on a conveyor apparatus, with the crabs being suspended from hooks. The crab legs are automatically cleaned as they are conveyed through a cleaning station having a pair of elongate, counter-rotating brushes between which the crab legs are passed. The brushes described in applicants' said co-pending applications comprise generally conventional bristle-bearing brushes, which are affective for removal of most foreign objects and debris from the other crab leg sections. However, the shells of crab and other crustaceans frequently have encrusted on them barnacles or other like foreign objects which very firmly adhere to the shells and cannot be removed by conventional brushes. Barnacles in particular are difficult to dislodge but must be removed if the seafood is to be saleable. Barnacles represent a particular problem in some catch locations. Crab legs are typically contaminated with barnacles on the upper (red) sides of the legs, and this presents both a commercial imperative to remove the barnacles from this most visible of locations, and a technical challenge to remove the barnacles without abrading or otherwise damaging the relatively delicate red layer. The barnacles can vary in size from approximately 2 mm to 10 mm in diameter. The concentration of barnacles that are attached to the shell varies depending on catch location.
The current method for removal of barnacles and the like consists simply of manual removal with a knife or other scraping tool. In this method, the barnacles are normally removed one at a time, and the method is correspondingly slow, labor intensive and expensive.
The cleaning apparatus of applicants' co-pending Canadian applications remove a portion of barnacles from crab leg shells. Typically, between three and five percent of barnacles are removed by this apparatus. Accordingly, it is desirable to provide an effective automated barnacle removal apparatus.
Various cleaning apparatus have been proposed for removal of debris from crustacean and shellfish shells. For example, Canadian Patent 2,015,863 (Tillion) discloses an apparatus for cleaning mussel shells, with the cleaning being performed by an array of abrasive rollers that also serve to transport the mussels between components of the system. Canadian Patent 1,205,963 (Lockerby) discloses apparatus for cleaning crab shells by means of an array of chain-mounted brushes that brush debris from the crab bodies.
The present invention relies for its operation on the convenient fact that barnacle shells are relatively hard and brittle, while crab shells are relatively resilient. Accordingly, a percussive force may be used to shatter or break off a barnacle from a crab shell, while leaving the crab shell substantially undamaged. Properly applied, a percussive force is capable of removing all or substantially all barnacle shells from crab shells, while causing minimal damage or abrasion to the crab shells.